Thin metal wire can be inexpensively produced by making the wire directly from molten metal. Thin metal wire produced in this manner is characterized by retaining the physical properties peculiar to the metal used. Furthermore, such wires have utility with respect to electric and electronic parts, composite materials, and textile materials. Furthermore, such wires are capable of withstanding high tension relative to their small thickness. It is a highly promising material suitable for various industrial applications. If a thin metal wire obtained by superquenching has a circular cross section and an amorphous structure, a nonequilibrium crystalline structure, or a microcrystalline structure, it acquires many excellent chemical, electromagnetic, and physical properties. Therefore, such a wire will find acceptance for actual use in various fields.
The so-called liquid quenching method produces a uniform, continuous thin metal wire by extruding molten metal through a spinning nozzle. Before the extruded flow of molten metal is cut by its own weight or broken by vibration, the flow of molten metal is brought into contact with the surface of a solid roll in rapid rotary motion thereby quenching and solidifying the flow of molten metal. Various studies have been made and suggestions offered relating to this method. Since the cooling rate in this method is as high as about 10.sup.5 .degree. C./sec, this method has been found to be highly effective in stably producing a ribbon of amorphous metal, nonequilibrium crystalline metal, or microcrystalline metal. Unfortunately, this method is only capable of producing thin metal wire of flattened cross section and such a product is only suitable for special uses. A thin metal wire of a circular cross section cannot be produced by this method.
Japanese Patent Application (OPI) No. 135820/74 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") (corresponding to U.S. Pat. No. 3,845,805) discloses a method which can be used for producing a thin metal wire having a circular section. When the method is used for this purpose, it involves passing a flow of molten metal through a quenching zone formed of a liquid medium so as to solidify the flow of molten metal. The essential requirements for this method are (1) that, in the quenching zone, the flow of molten metal discharged through the spinning nozzle and the flow of the liquid cooling medium should run parallel and (2) that, in the quenching zone, the flow of molten metal discharged through the spinning nozzle and the flow of the liquid cooling medium should run at the same speed. Since the flow of the liquid cooling medium relies for its speed upon the gravitational attraction acting upon the medium itself, the highest possible speed is on the order of only 180 m/min and can never be increased beyond this level. It would be quite difficult to further increase the speed of quenching and solidification by this method.
In producing a thin metal wire of high quality having an amorphous structure, a nonequilibrium crystalline structure or a microcrystalline structure, it is
important that the flow of molten metal be quenched and solidified at a speed of at least 10.sup.4 .degree.C./sec. As described above, the flow of molten metal and that of the liquid cooling medium run parallel to each other and at the same speed within the quenching zone and this speed itself is slow. The cooling speed is too low to produce a thin metal wire of high quality having a circular cross section. Moreover, since the speed of the liquid cooling medium is slow and the kinetic energy (speed.times.mass) of the medium is consequently small, the flow of the liquid cooling medium and its surface are disturbed by colliding with the flow of molten metal discharged through the spinning nozzle and by the boiling, vaporization, and convection of the liquid cooling medium. Thus, a thin metal wire of high quality having an amorphous structure, a nonequilibrium crystalline structure, or a microcrystalline structure cannot be obtained in a diameter with a satisfactory uniform circular cross section and without size irregularity in the longitudinal direction.
Japanese Patent Application (OPI) No. 69430/76 discloses a method which cools and solidifies the flow of molten metal by contacting it with a coolant to produce a continuous metal filament having a uniform circular cross section. The angle of contact between the flow of the coolant and that of molten metal discharged through a spinning nozzle is limited to within 20.degree.. The flow speed, V (m/min), of the coolant is limited within the range of V.sub.m &lt;V.ltoreq.5/2V.sub.m [wherein V.sub.m denotes the speed (m/min) of the flow of molten metal discharged through the spinning nozzle]. This method is capable of appreciably reducing the impact of collision of the flow of molten metal with that of the coolant. However, the method is not capable of producing a very high cooling speed, because the flow of the molten metal and that of the coolant still run substantially parallel. Even though efforts have been made to alleviate the collision, this method cannot produce a metal filament of high quality having a satisfactory uniform circular cross section. The cooling rate involved in this method is still not sufficient for the purpose of cooling a metal which is capable of forming an amorphous structure or a nonequilibrium crystalline structure and which, therefore, calls for a high cooling rate. By this method, therefore, it is difficult to obtain a metal filament of high quality processing excellent chemical, electromagnetic, and physical properties and having an amorphous structure or a nonequilibrium crystalline structure.
Japanese Patent Application (OPI) No. 64948/80 discloses the so-called submerged rotary spinning method. This method cools and solidifies a flow of molten metal extruded through a spinning nozzle by leading the flow of molten metal into a rotary cylinder containing a coolant. Although the coolant rotates at a very high speed, the rotating body of this coolant is stabilized by the action of the centrifugal force acting thereon. Because of the high cooling rate, this method has been found to be a desirable way of producing, in a limited quantity, a metal filament of high quality having a circular cross section. In accordance with this method, since the centrifugal force is used to keep the coolant in the form of a layer within the rotary cylinder and also since the cooled and solidified metal filament is continuously wound up in a pile on the inner wall surface of the rotary cylinder, the depth of the layer of coolant, the filament winding speed, the temperature of the coolant, etc., are varied gradually with time. Therefore, for continuous voluminous production of a metal filament of high quality there may be many unsolved problems with respect to this matter. Since the size, particularly the width, of the rotary cylinder is limited, the operation is inevitably batchwise . Continuous production of the metal filament on a commercial scale, therefore, is extremely difficult. Moreover, since this method requires the use of one rotary cylinder as a rule for each spinning nozzle in use, the cost of equipment and the cost of power for the actual production are prohibitively high.